Data from: Adult frogs and tadpoles have different macroevolutionary patterns across the Australian continent

Developmental changes through an animal’s life are generally understood to contribute to the resulting adult morphology. A possible exception are species with complex life cycles, where individuals pass through distinct ecological and morphological life stages during their ontogeny, ending with metamorphosis to the adult form. Antagonistic selection is expected to drive low genetic correlations between life stages, theoretically permitting stages to evolve independently. Using the Australian frog radiation, we examine the evolutionary consequences on morphological evolution when life stages are under different selective pressures. We use morphometrics to characterise body shape of tadpoles and adults across 166 species of frog and investigate similarities in the two resulting morphological spaces (morphospaces) to test for concerted evolution across metamorphosis in trait variation during speciation. A clear pattern emerges: Australian frogs and their tadpoles are evolving independently; their drastically different morphospaces and contrasting estimated evolutionary histories of body shape diversification indicate that different processes are driving morphological diversification at each stage. Tadpole morphospace is characterised by rampant homoplasy, convergent evolution and high lineage density; the adult morphospace by contrast shows greater phylogenetic signal, low lineage density and divergent evolution between the main clades. Our results provide insight into the macroevolutionary consequences of a biphasic life cycle.

通常认为，动物一生中的发育变化会对最终的成体形态塑造产生影响。具有复杂生活史的物种或许是例外：这类生物在个体发育（ontogeny）过程中会经历截然不同的生态与形态学生活阶段，最终以变态发育形成成体形态。拮抗选择（antagonistic selection）被认为会导致不同生活史阶段间的遗传相关性降低，理论上允许各阶段独立演化。本研究以澳大利亚蛙类辐射演化类群为研究对象，探讨当不同生活史阶段承受不同选择压力时，形态演化所带来的进化后果。我们采用形态测量学（morphometrics）方法，对166种蛙类的蝌蚪与成体的体型特征进行表征，并分析二者所构建的形态空间（morphospaces）之间的相似性，以检验物种形成过程中，性状变异在变态过程中是否存在协同演化（concerted evolution）。研究结果呈现出清晰的规律：澳大利亚蛙类与其蝌蚪呈现独立演化的特征；二者差异显著的形态空间以及截然不同的体型分化演化历史推断结果表明，不同的演化过程驱动着各生命阶段的形态分化。蝌蚪的形态空间以广泛的同塑性（homoplasy）、趋同演化（convergent evolution）以及较高的支系密度为特征；与之相对，成体的形态空间则展现出更强的系统发育信号（phylogenetic signal）、较低的支系密度，且主要演化支（clades）间呈现趋异演化。本研究结果为理解两阶段生活史的宏观演化后果提供了新的视角。